Project summary Tumors employ a number of mechanisms to promote immune escape, including the infiltration of different immunosuppressive cells in the tumor microenvironment such as T-regulatory cells (Treg). However, the specific signals within tumor cells that regulate the recruitment of Tregs, giving rise to tumor-induced immunosuppression, remain elusive. Based on our new preliminary data, we hypothesize that WEE1, an important regulator for cell cycle checkpoints, maintains an immunosuppressive and pro- tumorigenic microenvironment, and suppressing WEE1 activity, including via a clinically relevant WEE1 inhibitor, may be therapeutically beneficial by boosting immune-mediated tumor clearance. This proposal seeks to characterize the novel regulatory perspectives of WEE1-mediated crosstalk between tumor cells and host immune cells that should significantly forward the field. Specifically, this project is searching for the molecular mechanisms of WEE1-mediated Treg regulation and development of new effective combinatorial strategies. Our work will thus identify an unappreciated role of WEE1 inhibition in reversing tumor-induced immune suppression.